In 2016 the fall armyworm, a major pest in the Americas, was found in Africa for the first time. Since then it has rapidly spread across much of sub-Saharan Africa. The caterpillar feeds on more than 80 different plants, but maize is its preferred host, the most widely grown crop in Africa and a staple for half the continent. In the context of Africa’s climate, the insect is now likely to build permanent and significant populations in West, Central and Southern Africa, and spread to other regions when temperatures are favourable, posing a major threat to food security.